Metamath Proof Explorer

Theorem lt0neg2d

Description: Comparison of a number and its negative to zero. (Contributed by Mario Carneiro, 27-May-2016)

Ref Expression
Hypothesis leidd.1 
|- ( ph -> A e. RR )
Assertion lt0neg2d 
|- ( ph -> ( 0 < A <-> -u A < 0 ) )

Proof

Step Hyp Ref Expression
1 leidd.1 
 |-  ( ph -> A e. RR )
2 lt0neg2 
 |-  ( A e. RR -> ( 0 < A <-> -u A < 0 ) )
3 1 2 syl 
 |-  ( ph -> ( 0 < A <-> -u A < 0 ) )